I'm a recent graduate of MIT. Is there a grace period during which I can still purchase a new laptop with the student discount?

How long after I graduate will I be able to purchase a new laptop with a student discount?

The only requirement that MIT places on making purchases is the availability of a personal certificate. If you have a personal certificate, you can enter the online catalog and make purchases. Typically, graduating accounts are not deactivated until January (give or take). So, you should be able to generate a certificate until then.